Systems Used To Remove Air Blog
Systems Used To Remove Air
How to Remove Trapped Air from Your Heating and Cooling System
Trapped air in hydronic heating and cooling systems is a common cause of reduced efficiency, noisy operation and even component failure. Removing this air is crucial for maintaining peak performance. In this guide, we cover the different types of air removal devices and how to use them.
Why Remove Air From Your Heating and Cooling System?
Air in your hydronics system can cause:
- Reduced Heat Transfer – Air pockets act as insulators, preventing hot or cold water from reaching radiators or fan coils.
- Noisy Operation – Gurgling, banging and whistling sounds are often caused by air moving through pipes.
- Corrosion – Oxygen in the air accelerates corrosion within pipes, boilers and other critical components.
- Pump Failure – Air locks can cause circulating pumps to overwork and fail prematurely.
Types of Air Bubbles and How to Remove Them
There are two main categories of air problems, each requiring a specific solution:
For Larger Air Bubbles and Pockets
These are large pockets of air that collect at the high points of your system, such as the tops of radiators or vertical pipes.
Manual Air Vents (Manual Bleeder Valves)
- What they are – Simple, hand-operated valves, typically found on radiators.
- How they work – You open the valve with a key or screwdriver to release the trapped air until water squirts out.
- Best for – Periodic, manual bleeding of radiators and other terminal units.
Automatic Air Vents
- What they are – Self-operating valves with an internal float mechanism.
- How they work – As air collects in the valve's chamber, the float drops and opens a vent to release the air. When water re-enters, the float rises and seals the valve.
- Best for – High points in the system (like the top of risers) where air naturally accumulates, ensuring continuous, hands-free operation.
For Micro-Bubbles
Micro-bubbles are tiny and suspended in the water flow, making them impossible to remove with standard vents, so an air separator is needed.
Air Separators
- What it is – A device installed on the main pipeline that actively removes micro-bubbles.
- How it works – The water slows down inside the separator. A special internal mesh or polymer media (coalescence media) causes the micro-bubbles to collide and merge into larger bubbles. These larger bubbles rise to the top of the separator, and an integrated automatic air vent expels the collected air.
- Best for – Completely purging a system and maintaining air-free operation, which is critical for efficiency and longevity.
Key Differences – Air Vents vs. Air Separators
There are a few key differences between manual and automatic air vents and air separators.
How to Install an Air Separator Correctly
Proper placement is critical for an air separator to work effectively. Install it where the water temperature most affects the gas solubility.
- In Heating Systems – Install on the supply line, immediately after the boiler outlet. Hot water from the boiler releases dissolved gases more easily.
- In Cooling Systems – Install on the return line, just before the chiller inlet. Warmer return water releases dissolved gases more readily than the chilled water.
A Special Case – Water-Glycol Systems
Systems using a water-glycol antifreeze mixture (common in heat pumps, solar thermal and snowmelt systems) are especially prone to trapped air due to the fluid's higher viscosity. Using an air separator is highly recommended in these applications to ensure proper deaeration.
FAQs
How do air separators work?
Air separators work by using a combination of velocity reduction and coalescing media to separate air from a fluid. As the fluid enters the device, its velocity slows down, allowing air bubbles to rise to the top and be released through an automatic or manual air vent.
Where should I install an air separator?
In heating systems, an air separator should be installed on the supply line, right after the heat source, where the water is hottest and holds the least dissolved air. In cooling systems, install the air separator on the return line, just before the chiller inlet, where the water is warmest from collecting heat from the building.
How do manual air vents on radiators work?
Manual air vents work by opening a small valve at the top of the radiator to allow trapped air to escape, which is typically done with a radiator key. This process is called "bleeding" the radiator and helps make the radiator run more efficiently.
How do automatic air vents on radiators work?
Automatic air vents work by using a float to release trapped air, resealing to prevent water loss automatically. When air collects in the radiator, it causes the float to drop and open the valve, letting the air escape without the need to bleed off the trapped air manually.
I have a high-temperature application. Can I fit a standard automatic air valve?
Our standard automatic air valve range has a maximum tolerance of 110-120°C, depending on the model. However, we also offer a solar range that accepts a higher 160°C temperature and a glycol mix.